With age, a human crystalline lens opacifies (cataract) disabling the eye in generating a clear, well contrasted image. The only therapeutic solution to this problem is surgical replacement of the crystalline lens with an artificial intraocular lens (IOL). An IOL typically has two major components, a central lens or optic, and haptics. The IOL can be made of relatively rigid materials, such as polymethylmethacrylate (PMMA) or soft materials for foldable IOLs, such as silicone, soft acrylics, hydrogels and others.
The natural lens is removed from the capsular bag prior to insertion of the IOL. However, there are always residual lens epithelial cells (LECs) which remain attached to the remaining portions of the anterior capsule and to the equatorial portions of the lens capsule at the conclusion of the surgical procedure. These remaining LECs reproduce and migrate across the posterior capsule and undergo lens fiber regeneration and epithelial-to-mesenchymal transition. This shows up as a thickening, opacification and clouding of the posterior lens capsule, which may compromise visual acuity.
In addition, opacification of the anterior lens capsule can occur. This may lead to contraction of the capsulorhexis opening, and in extreme cases to phimosis. In cases of asymmetric or phimotic contraction, the IOL might move along the optical axis, causing change in refraction or causing a decrease in visual acuity.
As an additional side effect of the cataract surgery, a posterior vitreous detachment (PVD) might occur. PVD is a condition of the eye in which the vitreous gel separates from the retina. Although this does not directly threaten vision, the interaction between the vitreous body and the retina might play a decisive role in the development of major pathologic vitreoretinal conditions.